Method and structure for uniform contact area between heater and phase change material in PCRAM device

Abstract

A PCM (phase change memory) cell in a PCRAM (phase change random access memory) semiconductor device includes a phase change material subjacently contacted by a heater film. The phase change material is formed over a surface that is a generally planar surface with at least a downwardly extending recess. The phase change material fills the recess and contacts the upper edge of the heater film that forms the bottom of the recess. After a planar surface is initially formed, a selective etching process is used to recede the top edge of the heater film below the planar surface using a selective and isotropic etching process.

1. A semiconductor device comprising a PCM (phase change memory) cell comprising:
 a phase change material disposed on an upper surface of a dielectric having a heater therein, said heater including an oxide core having a top surface end a heater film disposed alongside and laterally surrounding said oxide core and extending upwardly and terminating in an indentation recessed below said upper and top surfaces, a top edge of said heater film forming a bottom of said indentation and said phase change material further disposed on said top edge and filling said indentation and said heater film further extending directly beneath a bottom surface of said oxide core. 
 
   
   
     2. The semiconductor device as in  claim 1 , wherein said top surface and said upper surface are coplanar. 
   
   
     3. The semiconductor device as in  claim 1 , further comprising a current source contacting said heater film. 
   
   
     4. The semiconductor device as in  claim 1 , wherein said indentation extends about 100-200 angstroms below said upper and top surfaces. 
   
   
     5. The semiconductor device as in  claim 1 , wherein said indentation is defined by sides that are sloped with respect to said upper surface. 
   
   
     6. The semiconductor device as in  claim 1 , wherein said phase change material comprises Ge 2 Sb 2 Te 5 . 
   
   
     7. The semiconductor device as in  claim 1 , wherein said lop surface is coplanar with said upper surface and said indentation is formed between said oxide core and said dielectric, said heater film directly interposed between said oxide core and said dielectric. 
   
   
     8. The semiconductor device as in  claim 1 , wherein said heater film that further extends directly beneath said bottom surface of said oxide core, directly contacts a subjacent conductive plate. 
   
   
     9. The semiconductor device as in  claim 1 , wherein said heater changes a phase of said phase change material from amorphous to crystalline or vice versa. 
   
   
     10. The semiconductor device as in  claim 1 , wherein said heater film comprises TiN. 
   
   
     11. The semiconductor device as in  claim 1 , further comprising a bottom conductive plate disposed below said dielectric and contacting said heater film and a conductive structure overlying and contacting said phase change material.